Engine starter gearing



July 8, 1952 D. l.. MILLER ENGINE STARTER GEARING Filed March 25, 1951 INVENToR. @mah/{Wallerl A onNL'Y WITNESS:

Patented July 8, 1952 lENGINE STARTER GEARING l Donald L. Miller, Horseheads, N. Y., assigner to `Bendix Aviation Corporation, a corporation of Delaware Application March 23, 1951, seria1N0.21'1,275

(ci. 'zi-7) Claims.

The present invention relates to engine starter gearing, and more particularly to an automatically engaging and disengaging drive incorporating'a combined overrunning and overload slipping clutch. Y

It is an object of the present invention to provide a novel starter gear of this type which is a cc` 1n"pactl self-contained unit of small size relative to its torque transmitting capacity.

It is another object Yto provide such a device which' is efficient and reliable in Voperation while being simple and economical in construction.

Further objects and advantages will be' apparent from the following description taken in connection with the accompanying drawing in which Fig. 1 is a sidefelevation partly broken away and in section of a preferred embodiment of the invention showing the parts in idle position.

Fig. 2 is a similar view showing the parts in cranking position, and s Fig. 8 is a similar view showing the parts in the positions assumed in case of tooth abutment between the pinion and engine gear.

In Fig. 1 of the drawing there is illustrated a power shaft I on which a transmission member 2 is xedly mounted as by means of keys 3 and set screw 4. The transmission member is provided with a radial flange l5 having a plurality of lugs 6 extending from. the periphery thereof.

A driving clutch disc 'I is slidably mounted on the power shaft I and is provided with teeth 8 having inclined surfaces and with a plurality of lugs 9 extending radially from the clutch member. A barrel member I I is -mounted on the transmission member and driving clutch disc, and has a plurality of slots I0 slidably receiving the lugs B and 9 of said members. A light compression mesh-enforcing spring I2 is located between the transmission and driving clutch members urging them apart, and a lock ring I 3 in the interior of the barrel II limits the separation of said members.

A pinion I4 is slidably journalled on the power shaft for longitudinal movement into and out of mesh with an engine gear I5. A screw shaft I6 is rigidly mounted in any suitable vmanner on the extended hub I'I of pinion I4, and a nut I8 threaded on the screw shaft I8 is slidably journalled within the barrel I I, being retained theref in by a terminal flange I9 of said barrel. Movement of the nut I8 away from' the flange I9 is` limited by a lock ring 2| in the interior of the barrel engaging a shoulder 22 on said nut.

Nut I8 is provided with teeth 23 having in- 2 clined surfaces4 corresponding to the teeth 8 of the driving clutch member 1, these teeth being normally held in light engagement by the spring I2. An anti-drift spring `24 surrounds the pinion I4, bearing at one end against the barrel flange I9 and at its other end seating in a counterbore 25 in the nut, so as to urge the screw shaft I6 to the left in Fig. 1, its travel being limited' by a shoulder 26 formed inthe 'nut I8 at the ends of the threads therein. A heavy compression spring 21, preferably formed, as illustrated, by a plurality of spring discs, is located between the transmission member 5 and driving clutch disc 7, said heavy spring being arranged to be engagedby the driving clutch disc after a predetermined amount of compression of the light spring-I2; after which the heavy spring 2l supplements the action of the light spring in strongly resisting further approach ofthe clutch disc toward the transmission member.

In operation, starting with the parts in the positions illustrated in Fig. 1, rotation of the power shaft I in the direction o f the arrow a by the starting motor, not illustrated, is transmitted through the transmission member 5 to barrel I I, to the driving clutch member 'I and through the teeth 8, 23 to the nut I8. The pinion I4 and screw shaft I6 are thereby traversed to the right until the pinion meshes with the engine gear I5, whereupon its movement is arrested by engagement of the screw shaft I6 with the barrel flange I9. The nut I8 and driving clutch member 1 are then moved backward by the screw-jack action of the nut and screw shaft, compressing the light spring I2 until the driving clutch member engages the heavy spring 21, after which further backward movement thereof is strongly resisted so that torque is built up to cause the pinion I4 to rotate the engine gear I5.

The torque so transmitted is limited by means of the stop ring 2l which arrests the backward movement of the nut I8. rFhereafter increasing torque causes the clutch teeth 8, 23 to wedge apart as illustrated in Fig. 2, and if the predetermined torque is exceeded, the clutch teeth will slip over each other by further compression of the spring 27, thus protecting the drive from excessive torque.

When the engine starts, the acceleration of the pinion I4 by the engine gear causes it to thread itself back to its normal position with the assistance of the anti-drift spring 24, thereby permitting the driving clutch member 'l to be returned by spring I2 to its normal position, where the lugs 9 seat against the ends 28 of slots l0. Since at this time the clutch teeth 8, 23 are held together only by the pressure of spring I2, the teeth 23 of the nut may overrun the teeth 8 of the clutch member so as to dissipate the momentum of the pinion and nut without causing any tendency to rebound toward the engine gear. In case during the meshing movement a pinion tooth should abut against a tooth of the engine gear as shown in Fig. 3, the movement of the pinion is arrested and the backward movement of the nut i8 compresses rst the mesh-enforcing spring I2, and thereafter the heavy cushion spring 21. When suicient torque has been built up to index the pinion teeth into proper registry with the tooth spaces of the engine gear, the spring l2 expands and snaps the pinion into initial engagement with the engine gear, after which meshing and cranking take place as shown.

Although but one embodiment of the invention has been shown and described in detail, it will be understood other embodiments are possible, and changes may be made in the design and arrangement of the parts without departing from the spirit of the invention.

Iclaim: n 1. In an engine starter drive a power shaft, a transmission member fixed'thereonhaving a radial flange, a driving clutch disc slidably rmounted on the shaft, a bar-rel member surrounding the Viiange and disc having means for preventing relative rotation of the flange and disc, and limiting separation thereof, a light compression spring on the shaft between the flange .and disc, a pinion slidably journaled on the shaft for movement into and out of mesh with an engine gear. a screw shaftxed on the pinion, a nut threaded on the `screw shaft slidably journaled in the barrel, means for limiting the longitudinal movement of -tne nut in the barrel; said driving clutch disc and` said nut having interengaging inclined clutch teeth; anda heavy compression clutch spring in the barrel supplementing thevaction of the light spring in resisting the approach of the clutch disc to said flange.

` in which the nut has an abutment limiting tele- Lil) scoping movement of the screw shaft therein, and including further a spring in the barrel urging the screw shaft-.toward idle position.

4. In an engine starter drive a power shaft, a transmission member fixed thereon, a driving clutch memberslidably mounted on the shaft, a light compression-spring between said members, a shorter stiff compression spring strongly resisting the approach of said members to each other,

-a pinion slidably journaledvon the power shaft,

a screw shaft xedly mounted on the pinion, a driven clutch-nut member threaded on the screw shaft, said clutch members Vhaving interengaging inclined clutch teeth, a barrel member enclosing the clutch members and screw shaft, having a splined vconnection with the transmission and driving clutch members and means cooperating therewith for limiting their separation, said barrel also having means for limiting longitudinal movement of the driven clutch member therein to an amountl substantially equal to the difference in length of the two springs., f A

5. A starter drive asset forth in claim 4 including. further yielding means normally holding the pinion telescoped within the barrel, said barrel having an abutmenty engaged by the screw shaftv to define, the meshing positionv of the pinion.

DONALD L. MILLER.

VNo references cited. 

